2,3,3,3-tetrafluoropropene (CF3CF═CH2, HFO-1234yf) is expected to be a new refrigerant which is less influential over the environment.
As a process for producing HFO-1234yf, a process has, for example, been proposed wherein 1,1-dichloro-2,3,3,3-tetrafluoropropene (CF3CF═CCl2, CFO-1214ya) and hydrogen gas are reached at a temperature of from 100 to 400° C., preferably from 125 to 350° C., in the presence of a catalyst having palladium supported on alumina (Patent Document 1).CF3CF═CCl2+2H2→CF3CF═CH2+2HCl  (1)
In the reaction of the formula (1), a large amount of hydrogen chloride is generated, and it is usual to neutralize and remove the hydrogen chloride by blowing, into an alkali aqueous solution, the formed gas containing HFO-1234yf and hydrogen chloride, discharged from the reactor.
However, in the reaction of the formula (1), 1,1,1,2-tetrafluoropropane (CF3CHFCH3, HFC-254eb) is formed as a byproduct, and when the formed gas is blown into an alkali aqueous solution, a dehydrofluorination reaction of HFC-254eb may take place by the alkali serving as a catalyst, to form 3,3,3-trifluoropropene (CF3CH═CH2, HFO-1243zf). HFO-1243zf has a boiling point close to HFO-1234yf and therefore cannot be separated therefrom by the subsequent distillation. Therefore, in HFO-1234yf as the product obtained by distillation, HFO-1243zf remains as an impurity, thus leading to deterioration of the quality of HFO-1234yf.